Deep CCD photometry in globular clusters. I. The Main sequence of M4

Journal Article · Wed Feb 01 04:00:00 EST 1984 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/161688· OSTI ID:6742199

Richer, H B; Fahlman, G G

From deep UBV CCD images obtained with CTIO 4 m telescope, we have constructed color-magnitude and color-color diagrams in a 4' x 3' field of the globular cluster M4. Inspection of the color-magnitude diagram indicates that the main sequence down to almost 3 mag below the turnoff has an intrinsic width no wider than +- 0.02 magnitudes in (B--V) implying that the variation in helium abundance (..delta..Y) in these stars must be less than +- 0.07 (..delta..Z = 0) or that the fractional variation in metallicity (..delta..Z/Z) is no larger than +- 0.22 (..delta..Y = 0). To a similar limit on the main sequence, the binary frequency in the field studied must be very small and does not exceed 3% of all main-sequence stars (and may be zero). The luminosity function of M4 is rather flat and definitely turns over by V = 20 (M/sub v/ = 7.5).

• Research Organization: Department of Geophysics and Astronomy, University of British Columbia
• OSTI ID: 6742199
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 277:1; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640102* -- Astrophysics & Cosmology-- Stars & Quasi-Stellar
Radio & X-Ray Sources
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABUNDANCE
CHEMICAL COMPOSITION
DIAGRAMS
ELEMENTS
FLUIDS
GASES
HELIUM
HERTZSPRUNG-RUSSELL DIAGRAM
MAIN SEQUENCE STARS
NONMETALS
PHOTOMETRY
RARE GASES
STAR CLUSTERS
STAR EVOLUTION
STARS